Drills are used in many fields, from carpentry to dentistry, and must be used with care, lest the drill make a hole which cannot be repaired. This is especially true in medical fields, where the surface to which the drill is applied is that of a living creature, and an improperly drilled hole may have catastrophic and irreparable consequences.
There is thus always a concern in using drills, and especially in using medical drills, that any plan for drilling is based on the best and most accurate information available, and that any drilling be done only after the procedure is planned down to the smallest detail. For example, X-rays may be taken of a patient's leg to determine the location of a fracture, so that setting pins may be inserted correctly and with minimum invasiveness.
Another application, and one with which the invention is primarily focused, is in the field of dental drilling and implants. In this field, it is customary for a dental surgeon to take X-rays of a patient's jaw prior to surgery and plot out carefully where an implant will be located. Known systems involve taking radiographic pictures of a patient's jaw, and determining, based on the radiograph, precisely where a hole will be drilled, how deep the hole will be, at what angle, and with what diameter. It is customary to make an impression of a patient's jaw, and then use that impression to make a template of the planned hole, with a guide for where the surgeon should drill.
These known systems, while mostly effective, also suffer from some drawbacks.
For one, when depending upon radiographs, such as X-rays, some imprecision may result from scatter caused by pre-existing dental work, such as amalgams or crowns, in the patient's mouth. Even small amounts of scatter may affect the accuracy of the resulting picture of the patient's jaw, and therefore lessen the accuracy of the resulting template.
A prior United States Patent Application, Ser. No. 2005/084144 entitled Oral Implant Template, the disclosure of which is hereby incorporated by reference, sought to address some of these deficiencies. This application describes the use of a process by which a Computed Tomography (“CT”) scan is made of a patient wearing a radiographic template on the jaw. The radiographic template carries a plurality of radiographic markers. After the scan of the jaw is obtained, a second scan is made of the radiographic template alone. The two data sets are then merged by using the radiographic markers as points of alignment. The result is that the radiographic template has the memory of the negative impression of the teeth which is registered in the CT scan data and allows for a replication of the tooth form with an accuracy that would otherwise be unobtainable. Based on the image and information thus obtained, the practitioner decides on the appropriate trajectory and location of the dental implant. With this data, the radiographic template is converted into a virtual surgical template with appropriate trajectories positioned at the correct locations where drilling guideways for the dental implants will be placed. Holes are indicated in the virtual surgical template at the desired locations and at the desired trajectories into which metal sleeves are inserted to guide the surgeon in the procedure. The virtual surgical template is then used to manufacture a surgical template which is inserted in the patient's mouth for precise placement of dental implants in the jaw bone via a drilling and insertion procedure.
This resulting surgical template forward from the virtual template, while offering an improvement over the prior art, still suffers from some drawbacks. For example, it provides no means for limiting the depth of penetration of the drill into the target surface. Particularly in the field of dental implants, where the target surface is a human jawbone, controlling the depth of penetration of the drill is of vital importance.
The inventor herein has prior patents in the field of stops for dental drill bits, for example U.S. Pat. Nos. 5,888,034 and 5,746,743, the disclosures of which are hereby incorporated by reference. These patents disclose various forms of stops for drill bits for limiting the depth of penetration of drill bits into a surface, especially dental drill bits used to limit the depth of penetration of dental drills into the human jaw. These patents also describe the use of an adjustable sleeve and ferrules to limited the depth of penetration of a drill bit and accommodate different drill diameters and lengths. Furthermore, the insertion of ferrules of different diameters allows the use of a single surgical template with drill bits of varying diameters, rather than a series of surgical templates with different guide sleeve widths which saves considerable cost.
These patents, however do not disclose any means for producing a drilling template for use in preparing for drilling into a surface.